The well known aerosol dispensing package has achieved wide acceptance and success. At present, a great number of products are distributed in aerosol packages, many of the products being heretofore deemed unsuitable for aerosol dispensing. To name a few, paints, insecticides, beauty aids, powders, food products, window cleaners, etc., have all undergone revolutionary packaging changes and are now dispensed in aerosol packages. In a conventional aerosol dispensing package, a rigid tubular member, usually of metal, is partially filled with the product to be dispensed and a dispensing valve is attached to the open end of the package. Thereafter, a suitable propellent in the form of a gas is introduced into the package which exerts a force against the product tending to urge the product out of the package through the dispensing valve. Upon actuation of the dispensing valve, the force exerted by the propellent will urge the product from the aerosol package in the form of a fine mist or spray.
Since the foregoing described aerosol packages have achieved great acceptance in the consumer market and enjoy a high degree of success, increasing effort has been directed to the fabrication of packages of this type. In the matter of economics, the success of the item is diminished or even eradicated if the cost of the dispensing package is out of proportion to the cost of the product to be dispensed. That is to say, the convenience of an aerosol package may be overridden by economic considerations when, for example, a twenty cent package is employed to dispense five cents worth of material.
Aerosol packages take many and varied forms and a primary consideration is the possible reaction between the propellent and the product to be dispensed. In many cases relating to the dispensing of non-edible products, the selection of the propellent receives little attention. However, in the packaging of volatile products, highly reactive products, edible products, etc., much attention may be directed to the selection of the propellent since reactions between the propellent and the product may oftentimes occur. This reaction results in contamination and degradation of the product and as such, is, of course, highly undesirable and to be avoided.
Accordingly, the need has arisen for a barrier package which will maintain the propellent separated from the product and a surrounding, usually rigid, container body.
One approach is by use of a piston. This has not proved satisfactory because of the possibility, during handling, of the package becoming dented. Another approach involves the use of an elastic inner container forming a barrier between the product and the pressure fluid. Two examples of this approach are U.S. Pat. Nos. 3,393,842 and 2,953,304, both of which utilize a product filled bag the rim of which is clamped between metal parts of the package. Difficulty has been encountered in insuring a complete seal as the bag may be cut during assembly.
The other examples are U.S. Pat. No. 3,189,231 and 3,415,425, in which the product is contained in the package above an initially compacted and folded expansible barrier containing the pressure fluid. The first of these patents indicates the need of a piston as well as the barrier, with attendant increase in package size. Another example is U.S. Pat. No. 3,549,058 wherein the metal package receives a liner having corrugated walls and a neck portion which fits into the neck of the package. While a rather complete liner is provided, difficulty is encountered in assembly as the liner neck sometimes slips into the package when the dispensing valve closure is secured. Examples of other barrier packages include 3,145,884; 3,393,842; and 3,541,581.
To date, barrier packages have had but limited commercial success which can be attributed at least in part to the differences in manufacturing, evidenced by high package failure rates and excessive package costs.
One difficult problem inherent in barrier dispensers involves premature closure of the outlet valve by the barrier so as to prevent full evacuation of the product, that is, a portion of the barrier may be forced over the outlet opening before all of the product has been discharged so that the remaining portion of the product is entrapped.
A second problem inherent in barrier dispensers involves permeability of the barrier. The nature of the barrier materials used, the propellents used, and the products to be dispensed require extensive efforts to avoid or reduce permeability. In addition, many of these products are required to have shelf lives in excess of 24 months.
A third problem inherent in barrier dispensers involves the integrity of the barrier under various conditions including filling and drop testing.